This invention relates generally to removing a nonsoluble oil from an aqueous solution used as a coolant in a machining environment. More particularly, this invention relates to a skimmer which removes a quantity of liquid mixture from the surface of the liquid mixture inside a tank containing the mixture and pumps the mixture to a coalescer which separates the tramp oil from the aqueous solution and returns the aqueous solution to the tank so that the useful life of the aqueous solution may be prolonged.
In many machining operations, an aqueous coolant is sprayed or flowed at the location where a cutting tool engages the workpiece, for lubrication and cooling purposes. The coolant is then collected in a tank located below the machine and recycled for continuous use for as long as possible.
Aqueous coolants of this type are fairly expensive, so it is advantageous to maintain such aqueous coolants in usable condition for as long as possible. Typical machining operations also include lubricating oil for lubricating movable parts. Eventually, this oil drips or flows into the aqueous coolant tank, where it floats upon the surface of the aqueous coolant due to its lighter weight and lower density. This oil, referred to as xe2x80x9ctramp oil,xe2x80x9d will eventually also contribute to bacterial growth within the aqueous coolant, resulting in a foul odor and reducing the useful life of the aqueous coolant.
Due to environmental concerns, the oil-contaminated aqueous coolant must be treated as hazardous waste, and therefore represents an environmental and economic concern. Thus, tramp oil represents a serious environmental and economic problem with respect to maintaining proper and cost effective aqueous coolant use during machining operations.
A number of skimming devices have been developed over the years to remove tramp oil from the surface of aqueous coolant in a coolant tank for a machine. Disk skimmers include a disk which extends into the aqueous coolant and into contact with the tramp oil. Rotation of the disk near the surface results in removal of some oil from the surface, whereupon it is scraped by a blade and removed. Belt type skimmers involve an endless belt which removes tramp oil from the surface of the aqueous coolant, whereupon it is also scraped therefrom for removal. Disk and belt skimmers of this type are relatively inefficient and have space limitations for proper mounting and operation.
Floating tube skimmers and weir-type skimmers adapt to liquid level fluctuations, and they generally include a pump for pumping the skimmed liquid to a separation device. Such skimmers have proved to be acceptable in relatively large bodies such as lakes, ponds, rivers or even oceans. However, their size typically prevents their use in machining applications. In machining operations, most coolant tanks are as shallow as five or six inches, or as deep as several feet. Also, some machining coolant tanks are located in relatively inaccessible places without much spare space located adjacent thereto.
In summary, in machining operations it is necessary to skim primarily tramp oil from the surface of the aqueous coolant in the tank (though the skimmed liquid will also include some coolant), to deliver the tramp oil coolant mixture to a separation unit, to separate the tramp oil from the aqueous coolant for collection, and to return the aqueous coolant to the tank for reuse.
Applicant""s U.S. Pat. No. 5,601,705 discloses a two-part system including a skimmer located inside a tank containing a liquid mixture and a coalescer located outside the tank. The skimmer skims the liquid mixture from the surface of the liquid mixture inside the tank. The coalescer includes a pump which pumps the skimmed fluid through a hose from the skimmer to the coalescer. The coalescer separates tramp oil from the mixture and returns xe2x80x9ccleanedxe2x80x9d coolant to the tank. Although U.S. Pat. No. 5,601,705 discloses one configuration or design of coalescer, the coalescer may take numerous configurations such as the one disclosed in applicant""s U.S. Pat. No. 6,056,128.
Although the skimmer disclosed in U.S. Pat. No. 5,601,705 functions effectively, it has numerous parts which must be assembled in a certain manner, which is very time-consuming. Therefore, some may consider it too expensive to manufacture and too difficult to maintain in the event one or more parts fails.
Therefore, It is an object of this invention to reduce the number of parts of an aqueous coolant skimmer, specifically the number of moving parts and to simplify the manufacture of such a skimmer.
It is another object of this invention to improve access to the parts of an aqueous coolant skimmer, to make it easier maintain, without sacrificing the primary functional features of applicant""s prior devices.
It is another object of this invention to enable the purchaser of an aqueous coolant skimmer to repair the skimmer including replacing the pump without sending the skimmer back to the manufacturer for repair.
It is still another object of the invention to achieve the above-noted objects for a variety of differently sized and shaped tanks for collecting and holding aqueous coolant.
The present invention achieves the above-stated objects by utilizing a floatable skimmer which floatably adjusts to the level of the liquid mixture in the tank while at the same time skimming liquid from adjacent the surface, a bracket located at a fixed vertical level in the tank and operatively connected to a vacuum source, and an outlet tube which conveys skimmed liquid from the skimmer to the pump due to the application of vacuum from the vacuum source, the outlet tube adapted to accommodate relative vertical movement between the floatable skimmer and the bracket.
Another aspect of the invention further contemplates a pair of spaced arms or connectors, each being pivotably connected at both ends, to the bracket and to the skimmer. These connectors assure stable relative vertical movement between the floatable skimmer and the bracket as the liquid level in the tank fluctuates up and down. These connectors also maintain a desired distance between the skimmer and the bracket.
The invention also contemplates, as the vacuum source, the use of a submersible pump located along an outflow line or conduit. The pump preferably mounts to the bracket and the outflow conduit resides in fluid communication with one end of the outlet tube. Thus, the apparatus pumps skimmed liquid from the supply container, through the outlet tube, along the outflow conduit and eventually to a coalescer.
The skimmer includes an open-top supply container with a variably sized inlet which adjusts in response to level liquid within the supply container, the supply container further having an outlet adjacent a bottom thereof, which is in fluid communication with one end of the flexible outlet tube. An adjuster residing within the open-top supply container floatably adjusts the size of the inlet in response to the level of the liquid within the supply container, so that the variation of the flow rate of the pump produces a corresponding change in the size of the cross sectional area of the inlet to the supply container. More specifically, an increase in the flow rate of the pump causes the adjuster to correspondingly increase the size of the inlet, while a decrease in the flow rate of the pump causes a corresponding decrease in the size of the inlet.
Overall, compared to applicant""s prior skimmer, the present invention significantly reduces the number of parts. This reduction in the number of components also simplifies the overall construction. Moreover, because of its inventive structure, the parts are simpler in construction, and the parts are more accessible for an operator, and thereby easier to maintain and/or replace.
If the pump is mounted directly to the bracket, the pump resides immediately adjacent the skimming apparatus and within the tank. This arrangement helps to further simplify the overall construction of the coalescer, which is typically mounted to a nearby wall. Nevertheless, while a preferred embodiment the present invention contemplates a submersible pump connected directly to the bracket located in the coolant tank, it is to be understood that the pump could be located anywhere along the fluid connection between the outlet tube and the coalescer, so long as sufficient fluid pressure is maintained in the fluid line connection therebetween.
In an alternative embodiment of the present invention, the skimming apparatus is not secured to a tank wall. Rather, the skimming apparatus is secured to a support float which rises and lowers with the level of fluid inside the tank. This embodiment is preferably used inside deep tanks but may be used in any size of tank.
These and other features of the invention will be more readily understood in view of the following detailed description and the drawings.